Oil retention and delivery system for a bearing

ABSTRACT

A bearing seal assembly of a rotary machine includes and inner shaft and an outer shaft. The outer shaft is disposed concentrically around and radially outward from the inner shaft. The space between the inner and outer shafts forms an annulus void. The inner shaft includes an oil inlet port through which lubricating oil enters the annulus void. A grooved structure is located on an inner surface of the outer shaft, and the grooved structure is configured to retain oil upon shutdown of the rotary machine. A bearing is located outside of the outer shaft. An oil outlet port is disposed in the outer shaft and is connected to the grooved structure for supplying lubricating oil to the bearing.

BACKGROUND

The present disclosure relates generally to the field of bearingassemblies in rotary machines. In particular, the present disclosurerelates to the delivery of lubricating oil in bearing assemblies duringstart-up of the rotary machine.

Bearings in rotary machines usually require some type of lubricant toensure long life and proper function. Bearing lubrication is critical,especially in high speed, high load, or high temperature applications,such as an aircraft electrical power generator. Typically, most bearingwear occurs when the bearing first begins to rotate and is without oillubrication. In applications such as an aircraft generator or the like,the oil supply may be pumped to the generator from an oil circuit. Oildelivery to the machine may take some time to reach the bearing, orotherwise be delayed from providing lubricant to the bearing during thecritical startup period. Oil delivery to the bearing may be furtherdelayed if the machine is devoid of oil, if pump startup is retarded, orif time is required to establish sufficient oil circuit pressure beforeoil can flow effectively.

SUMMARY

A bearing seal assembly of a rotary machine includes and inner shaft andan outer shaft. The outer shaft is disposed concentrically around andradially outward from the inner shaft. The space between the inner andouter shafts forms an annulus void. The inner shaft includes an oilinlet port through which lubricating oil enters the annulus void. Agrooved structure is located on an inner surface of the outer shaft, andthe grooved structure is configured to retain oil upon shutdown of therotary machine. A bearing is located outside of the outer shaft. An oiloutlet port is disposed in the outer shaft and is connected to thegrooved structure for supplying lubricating oil to the bearing.

In a method of delivering lubricating oil to a bearing, during steadystate operation lubricating oil is supplied through an oil inlet port toan annulus void between an inner shaft and an outer shaft. Asubstantially continuous oil annulus is formed in a grooved structurelocated on an inner radial surface of the outer shaft. Lubricating oilis provided from the grooved structure through an oil outlet port in theouter shaft to the bearing during steady-state operation. Lubricatingoil is retained in the grooved structure during a shut-down state.Lubricating oil is then provided to the bearing from the groovedstructure through the oil outlet port during start-up of the rotarymachine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of a bearing seal assembly in arotary machine.

FIG. 2 is a cross-sectional side view of a bearing seal assembly in ashut-down state of a rotary machine.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional side view of bearing seal assembly 10.Bearing seal assembly 10 includes shaft assembly 12, bearing assembly14, and lubrication supply system 16.

Shaft assembly includes inner shaft 18, outer shaft 20, annulus void 22,lubricating oil LO, oil inlet port 24, first groove 26, second groove28, oil outlet port 30, and wall 32. Lubrication supply system 16includes external oil circuit 34, oil pump 36, oil feed tube 38, and oiltube jet 40. Bearing assembly 14 includes bearing balls 42, inner race44, outer race 46, oil passage 48, and bearing cage 50.

Outer shaft 20 concentrically surrounds inner shaft 18. In a preferredembodiment, no sustained relative motion exists between inner shaft 18and outer shaft 20. Inner shaft 18 is held in place relative to outershaft 20 by way of a spline and/or o-ring seal apparatus. Annulus void22 is formed between inner shaft 18 and outer shaft 20. Annulus void 22receives lubricating oil LO from inner shaft 18 through oil inlet port24 disposed in inner shaft 18. Outer shaft 20 includes first groove 26and second groove 28. First groove 26 and second groove 28 are locatedon an inner radial surface of outer shaft 20. First groove 26 isradially and axially aligned with oil inlet port 24. Oil outlet port 30is disposed in outer shaft 20 and is radially and axially aligned withsecond groove 28. Wall 32 is located between first groove 26 and secondgroove 28.

During steady-state operation of a rotary machine, inner shaft 18 andouter shaft 20 rotate and form annulus void 22 which receiveslubricating oil LO from oil inlet port 24. Lubricating oil LO flows toinner shaft 18 from lubrication supply system 16. Centrifugal forceinduced by the rotation of inner shaft 18, and oil pressure provided bylubrication supply system 16, feeds lubricating oil LO into annulus 22by way of oil inlet port 24 disposed in inner shaft 18. Centrifugalforce induced by the rotation of outer shaft 20 causes lubricating oilLO fed to annulus 22 to collect in first groove 26 and second groove 28located on an inner radial surface of outer shaft 20.

During steady-state operation of the rotary machine, first groove 26 isflooded with lubricating oil LO such that lubricating oil LO spills overwall 32 into second groove 28. Second groove 28 contains oil outlet port30 to feed lubricating oil LO to bearing balls 42. During steady-stateoperation of the rotary machine, lubricating oil LO flows substantiallyunimpeded to bearing balls 42. It is important to note that duringsteady state operation, centrifugal force exceeds gravitational force.Centrifugal force thereby maintains a continuous oil annulus in firstgroove 26 such that lubricating oil LO is allowed to pass over wall 32into second groove 28. Similarly, a concentric oil film is maintained insecond groove 28 to feed bearing balls 42 with lubricating oil LOthrough oil outlet port 30 and oil passage 48 in inner race 44.

First groove 26 and second groove 28 may include a circumferentialshape, or other shapes such as a spiral configuration. First groove 26and second groove 28 make up a grooved structure extending thecircumference of the outer shaft. Additionally, the grooved structuremay include only first groove 26 and can also include more than twogrooves.

Bearing assembly 14 is disposed outside of outer shaft 20. Bearing balls42 are positioned between inner race 44 and outer race 46. Inner race 44is located immediately adjacent to and radially outward from outer shaft20. Inner race 44 extends the entire outer circumference of shaftassembly 12. Bearing balls 42 are located immediately adjacent to andradially outward from inner race 44. Outer race 46 is locatedimmediately adjacent to and radially outward from bearing balls 42.Outer race 46 extends the entire outer circumference of shaft assembly12. Oil passage 48 is disposed in inner race 46 and extends the entirecircumference of shaft assembly 12. Bearing cage 50 is located on thetwo axial sides of bearing balls 42 and, similar to inner race 44 andouter race 46, bearing cage 50 extends the entire outer circumference ofshaft assembly 12.

Inner race 44 is pressed onto the outer surface of outer shaft 20. Innerrace 44, bearing balls 42, and bearing cage 50 rotate along with outershaft 20. Outer race 46 remains stationary to the world and does notrotate along with outer shaft 20. Oil passage 48 allows for fluidcommunication of lubricating oil LO from shaft assembly 12 to bearingballs 42.

The majority of lubrication supply system 16 is located outside of shaftassembly 12. In lubrication supply system 16, external oil circuit 34controls oil pump 36 which is in fluid connection with oil feed tube 38.Oil tube jet 40 is disposed on oil fed tube 38 on an end of oil feedtube 38 opposite from oil pump 36. Oil tube feed jet 40 is positionedinside inner shaft 18 along shaft centerline CL. Pressure from oil pump36 feeds lubricating oil LO through oil feed tube 38, out of oil tubejet 40, and into an inside diameter of inner shaft 18.

Bearing seal assembly 10 of the present disclosure significantly reducestime between rotary machine startup and lubrication of bearing balls 42.A portion of lubricating oil LO is retained in second groove 28 withinclose proximity to bearing balls 42 during machine shutdown. Retainedlubricating oil LO is delivered to bearing balls 42 during startupbefore sustained delivery of lubricating oil LO is established. Thefeatures of bearing seal assembly 10 incorporated on outer shaft 20cause some quantity of lubricating oil LO to be trapped in second groove28 during machine shutdown such that it may be delivered nearlyinstantly to bearing balls 42 during machine startup thereby minimizingthe time bearing balls 42 are without lubrication and preventing wear onbearing balls 42 until the steady state flow of lubricating oil LO isachieved.

Lubricating oil LO retained in second groove 28 is delivered to bearingballs 42 through oil outlet port 30 as soon as the rotary machine startsrotating during startup. This quantity of lubricating oil LO providessufficient lubrication for bearing balls 42 until steady-state flow oflubricating oil LO is reached.

FIG. 2 is a cross-sectional side view of bearing seal assembly 10 in ashut-down state. During shut-down of the rotary machine, centrifugalforce, which supports the oil annulus within first groove 26, begins todiminish. As centrifugal force decreases, the oil annulus in firstgroove 26 begins to break down. As machine speed reduces, the oilannulus once present in first groove 26 begins to redistribute itsvolume to the lowest area of first groove 26. Surplus lubricating oil LOat the bottom of first groove 26 spills over wall 32 and collects insecond groove 28. During shutdown, lubricating oil LO is only drainedfrom second groove 28 as oil outlet port 30 in outer shaft 20 passesbottom dead center. Only in the unlikely event that oil outlet port 30happens to come to rest at the bottom dead center position willlubricating oil LO drain entirely from second groove 28. It is highlyprobable, however, that some quantity of lubricating oil LO will remainwithin second groove 28 when outer shaft 20 stops rotating.

The present disclosure provides a novel and non-obvious approach atimproving bearing lubrication during critical machine startup periodsbefore sustained oil can be delivered to the bearing, thereby increasingbearing life. By storing a quantity of oil proximate to the bearingpoint of use, lubrication to the bearing is nearly instantaneous due tooil retained within the shaft at shutdown.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A bearing seal assembly of a rotary machine includes an inner shaft andan outer shaft. The outer shaft is disposed concentrically around andradially outward from the inner shaft. The space between the inner andouter shafts forms an annulus void. The inner shaft includes an oilinlet port through which lubricating oil enters the annulus void. Agrooved structure is located on an inner surface of the outer shaft, andthe grooved structure is configured to retain oil upon shutdown of therotary machine. A bearing is located outside of the outer shaft. An oiloutlet port is disposed in the outer shaft and is connected to thegrooved structure for supplying lubricating oil to the bearing.

The bearing seal assembly of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components.

The grooved structure is configured to contain lubricating oil during asteady-state operation of the rotary machine.

The grooved structure is configured so that a centrifugal force of thelubricating oil maintains a substantially continuous oil annulus locatedin the grooved structure during steady-state operation of the rotarymachine

The grooved structure includes a first groove and a second groove.

A wall separates the first groove and the second groove.

The wall is configured so that excess lubricating oil in the firstgroove flows over the wall and into the second groove.

The oil outlet port is connected to the second groove.

A method of delivering lubricating oil to a bearing in a rotary machineincludes positioning an outer shaft concentrically around and radiallyoutward from an inner shaft. A bearing is located outside of the outershaft. Lubricating oil is supplied to an annulus void between the innerand outer shafts through an oil inlet port during steady-stateoperation. During steady-state operation, a substantially continuous oilannulus is formed in a grooved structure located on an inner radialsurface of the outer shaft. Lubricating oil is provided from the groovedstructure through an oil outlet port in the outer shaft to the bearingduring steady-state operation. At least a portion of the lubricating oilis retained in the grooved structure during a shut-down state.Lubricating oil is then provided to the bearing from the groovedstructure through the oil outlet port during start-up of the rotarymachine.

The method of delivering lubricating oil of the preceding paragraph canoptionally include, additionally and/or alternatively, any one or moreof the following steps, features, configurations and/or additionalcomponents.

The outer shaft rotates with a speed that produces a centrifugal forcelarge enough to contain the lubricating oil within the grooved structureduring steady-state operation.

The grooved structure includes a first groove and a second groove.

The first and second grooves are separated by a wall.

The excess lubricating oil in the first groove flows over the wall andinto the second groove.

The oil outlet port is connected to the second groove.

The invention claimed is:
 1. A bearing seal assembly of a rotarymachine, the bearing seal assembly comprising: an inner shaft; an outershaft disposed concentrically around and radially outward from the innershaft, wherein a space between the inner shaft and the outer shaft formsan annulus void; an oil inlet port in the inner shaft through whichlubricating oil can enter the annulus void; a grooved structure disposedin an inner radial surface of the outer shaft, wherein the groovedstructure forms an oil retaining reservoir configured to retain alubricating oil upon shutdown of the rotary machine, further wherein thegrooved structure is configured to contain lubricating oil during asteady-state operation of the rotary machine, and further wherein thegrooved structure is configured so that a centrifugal force of thelubricating oil maintains a substantially continuous oil annulus locatedin the grooved structure during steady-state operation of the rotarymachine; a first groove and a second groove included in the groovedstructure; a first portion and a second portion included in the firstgroove, the first portion having a larger radial diameter than thesecond portion; rolling elements located external to the outer shaft; aninner race positioned between the rolling elements and the outer shaft,wherein the inner race separates the rolling elements from the outershaft; and an oil outlet port disposed in the outer shaft and directlyfluidly connected to the grooved structure, the oil outlet portconfigured to supply the lubricating oil from the grooved structurethrough the inner race and to the rolling elements.
 2. The bearing sealassembly of claim 1, wherein a wall separates the first groove and thesecond groove.
 3. The bearing seal assembly of claim 2, wherein the wallis configured so that excess lubricating oil in the first groove flowsover the wall and into the second groove.
 4. The bearing seal assemblyof claim 1, wherein the first portion of the first groove has a largerdiameter than the second groove.
 5. The bearing seal assembly of claim1, wherein the inner race includes an oil passage fluidly connecting theoil outlet port and the rolling elements.
 6. The bearing seal assemblyof claim 5, wherein the oil passage is positioned in axial alignmentwith the oil outlet port.
 7. The bearing seal assembly of claim 5,wherein the inner race and oil passage extend along a circumference ofthe outer shaft.
 8. A method of delivering lubricating oil to a bearingin a rotary machine, the method comprising: supplying the lubricatingoil during steady-state operation through an oil inlet port to anannulus void between an inner shaft and an outer shaft; forming asubstantially continuous oil annulus in a grooved structure duringsteady-state operation, wherein the grooved structure is located on aninner radial surface of the outer shaft, further wherein the groovedstructure is configured to contain lubricating oil during a steady-stateoperation of the rotary machine, and further wherein the groovedstructure is configured so that a centrifugal force of the lubricatingoil maintains a substantially continuous oil annulus located in thegrooved structure during steady-state operation of the rotary machine,further wherein the grooved structure includes a first groove and asecond groove, and further wherein the first groove includes a firstportion and a second portion, the first portion having a larger radialdiameter than the second portion; providing lubricating oil from thegrooved structure through an oil outlet port in the outer shaft andthrough an inner race to rolling elements during steady-state operation,wherein the inner race separates the rolling elements from the outershaft; retaining at least a portion of the lubricating oil in thegrooved structure during a shut-down state; and providing lubricatingoil to the rolling elements from the grooved structure through the oiloutlet port during start-up of the rotary machine.
 9. The method ofclaim 8, wherein during steady-state operation the outer shaft rotateswith a speed that produces a centrifugal force large enough to containthe lubricating oil within the grooved structure.
 10. The method ofclaim 8, wherein a wall separates the first groove and the secondgroove.
 11. The method of claim 10, wherein excess lubricating oil inthe first groove flows over the wall and into the second groove.
 12. Themethod of claim 10 and further comprising: passing lubricating oil fromthe first groove over the wall and into the second groove.
 13. Themethod of claim 8, wherein providing lubricating oil from the groovedstructure through the oil outlet port in the outer shaft and through theinner race to the rolling elements during steady-state operation furtherincludes passing lubricating oil through an oil passage in the innerrace.
 14. The method of claim 8, wherein providing lubricating oil tothe rolling elements from the grooved structure through the oil outletport during start-up of the rotary machine further includes passinglubricating oil through the inner race.